crushed spark plug

[sacrileger]

just bought a donor 94 eagle talon w/ 7-bolt 4g63 nt. the motor would start w/o hesitation but it would run extremely rough. it wouldnt idle. it would stall. the motor misfired badly. i had to keep the rpm above 1500 to keep it going. i took it for a short test drive, about 1 mile. even w/ a motor that sounded like it ran on 2-3 cylinders w/ extreme knock, i was able to get around in it. i was 99.99% certain the head gasket was blown. it wasnt.

i checked the compression (dry) and it read 185,175,175,175 (throttle closed). all spark plugs had heavy, black and wet deposits on them. it didnt appear to be oil and there were no signs that the motor burned oil. however, droplets of water were spitting out of the tail pipe.

i checked the coolant. it was clear. i checked oil. no coolant in oil; or under the valve cover. the only way i say that coolant would get into the motor and interfere w/ the fuel mixture, and caused it to misfire, was via intake manifold, i.e. hair line fracture in the intake coolant passages, or broken seal, and the vacuum would be sucking in coolant along w/ air/fuel mix. it had to be tiny since the engine would start and run; even though it misfired badly.

before i get to the punch line, i want you to keep this in mind: before i bought the car, i drove it. i revved the motor to at least 5-6000 rpm. while i had the car in garage and was diagnosing the problem, i started the motor countless times, i idled it, i revved it, sometimes as high as 6000 rpm. and no doubt the previous owner did the same - before and after the leak developed.

in any case, to solve this, or at least temporarily and partially, and at bare minimum to see if i am on the right track, i bought rislone liquid copper intake and radiator "stop leak". i poured about 200g directly into the cooling system.
i start the motor and idle it at about 1500rpm, while listening for any changes. after about 10 minutes, the temp rose to about 60-70c. then i hear this thump. and the motor stopped. i turned the motor w/ starter and heard more thumps. and then the motor seized up and wouldnt turn over.

i started taking the spark plugs out. i get to #2 and cant even turn the spark plug loose. with some force, i start taking it out feeling like i am stripping the thread. i take it out and it's smashed. below are some images.

it is clear that as much as i dont want to, i have to take the cyl head off to survey the damage, but before i do, i am asking you for feedback as to what happened before i destroy the evidence that would point to the cause of this. what is it that smashed the spark plug and why after the engine was run for that long? why after the rislone solution? or was that coincidental and it would've happened anyway. any ideas what to look for so this doesnt happen again?

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[GRAVEDIGGER]

Wow! What a story... Glad it is still running well for you!

 

[Murdertalon]

Holy shit. You are crazy, I am glad its still running. This is like some guys I know that used to use junk they found lying around the garage or junk yard to make their cars faster. I mean I am just surprised. I would have found another 1g piston, but you do you, if it works it works.

I would likely have taken the block out and apart / hot tank ect.. what a testament to how durable some of these engines ended up being - just running, not pushing 50psi of boost till it explodes. (this site is all about pushing 50# until it explodes) it seems like at times heh.